Which Corporate Tax Form to File for YA 2026? Free Form C-S and Form C Checker
Which corporate tax form to file depends on four IRAS tests. A Singapore-incorporated company with revenue of $5 million or below, only 17%-taxable income and no claims for loss carry-back, group relief, investment allowance, foreign tax credit or tax deducted at source may file Form C-S, or Form C-S (Lite) if revenue is $200,000 or below. Every other company files Form C, except dormant ones, which have a simpler form.
This guide is for directors and bookkeepers preparing Year of Assessment (YA) 2026 returns, which cover financial years ending in 2025 and are due by 30 November 2026. Amounts are in Singapore dollars (SGD), and the rules are as at November 2026.
Key takeaways
- Form C-S needs all four conditions. Form C-S (Lite) also needs revenue of $200,000 or below.
- Revenue means gross income from the principal activities, so fixed deposit interest is left out.
- Form C is filed with the financial statements and tax computation; Form C-S filers prepare and keep them instead.
- A dormant company files the simpler Form for Dormant Company, unless myTax Portal shows "No Business Done".
Table of Contents
- Form C-S Checker for YA 2026
- How IRAS Decides Which Corporate Tax Form to File
- Worked Examples
- Form C vs Form C-S: What Each Requires
- How to File in myTax Portal
- What If the Company Was Dormant?
- YA 2026 Deadlines and Extensions
- Common Mistakes When Choosing the Form
- When to Get Professional Help
- Frequently Asked Questions
- Official Sources
Form C-S Checker for YA 2026
Answer for the financial year that ended in 2025, the basis period for YA 2026. Follow-up questions appear only when your answer needs them.
Which corporate tax form should your company file?
YA 2026 returns, due by 30 November 2026. Rules as at November 2026.
How IRAS Decides Which Corporate Tax Form to File
Form C-S is IRAS's simplified Corporate Income Tax Return for small companies, and Form C is the full return. A company may use Form C-S only if it meets all four conditions below; otherwise it files Form C. Form C-S (Lite), the shorter version, is optional.
Form C-S and Form C-S (Lite) eligibility
| IRAS condition | What it means |
|---|---|
| 1. Incorporated in Singapore | Companies incorporated abroad, including their Singapore branches, file Form C. |
| 2. Revenue of $5 million or below | Gross income from the principal activities (see below). |
| 3. Only income taxable at 17% | No tax-exempt or concessionary-rate income, such as pioneer incentive income. One-tier exempt Singapore dividends and section 13(8) exempt foreign income are allowed. |
| 4. No excluded claims | No claim for loss carry-back, group relief, investment allowance, or foreign tax credit and tax deducted at source. |
| Form C-S (Lite) | Revenue of $200,000 or below, plus conditions 1 to 4. |
A tax loss does not rule out Form C-S, unless the company is in the business of making investments under section 10D of the Income Tax Act 1947. The start-up and partial tax exemptions do not count as exempt income either.
Group relief catches both companies: IRAS requires the transferor to submit Form GR-A and the claimant Form GR-B when filing Form C, and neither can use Form C-S or Form C-S (Lite).
How revenue is measured
Revenue is the gross income from the principal activities in the basis period. Separate-source income, such as fixed deposit interest or rent from real property, stays out, while an investment holding company uses its investment income. If a new company's first accounts cover more than 12 months, use the 12 months ending on the year end. In IRAS's example, a company incorporated on 15 April 2024 with a 30 June 2025 year end tests 1 July 2024 to 30 June 2025.
Revenue above $5 million for one year
A company that filed Form C-S for YA 2025 may file it again for YA 2026 even with revenue above $5 million, if every other condition is met. IRAS's FAQ does not mention Form C-S (Lite) separately; as it is a simplified Form C-S, we treat a YA 2025 Form C-S (Lite) filing the same way. This administrative concession covers temporary swings only. If revenue is still above $5 million for YA 2027, the company moves to Form C.
Worked Examples
Unless stated, each hypothetical company is Singapore-incorporated, has only 17%-taxable income and makes no excluded claims. The checker gives the same answers.
| Company | Facts for YA 2026 | Form |
|---|---|---|
| A: consultancy, December 2025 year end | Fees of $180,000 and fixed deposit interest of $1,200 | Form C-S (Lite): the interest is separate-source, so revenue is $180,000 |
| B: F&B company, March 2025 year end | Revenue of $1.4 million; claiming the start-up tax exemption | Form C-S: the exemption is not exempt income |
| C: distributor, June 2025 year end | Revenue of $5.6 million; filed Form C-S for YA 2025 | Form C-S under the concession, then Form C for YA 2027 if revenue stays above $5 million |
| D: group subsidiary | Revenue of $2.3 million; claiming group relief | Form C |
| E: Singapore branch of a Hong Kong company | Revenue of $400,000 | Form C |
| F: stopped trading in 2024 | Only $800 of fixed deposit interest in its 2025 financial year | Not dormant, because it had income: Form C-S (Lite), as revenue is below $200,000 |
| G: dormant since 2023 | No business or income; myTax Portal shows "Active" | Form for Dormant Company, or a waiver if it qualifies |
Next, estimate the tax with our corporate tax calculator.
Form C vs Form C-S: What Each Requires
The practical difference is what you send to IRAS.
| Form C-S (Lite) | Form C-S | Form C | Form for Dormant Company | |
|---|---|---|---|---|
| Fields | 6 essential | 18 | Full return | 2 essential |
| Financial statements | Prepare and keep | Prepare and keep | Submit | Not submitted |
| Tax computation | Prepare and keep | Prepare and keep | Submit, with schedules | Not submitted |
| Other documents | None, unless claiming section 19B allowances on IP | Same as Lite | Form IRIN 301, a detailed profit and loss statement and claim forms | None |
| YA 2026 due date | 30 November 2026 | 30 November 2026, or 15 December 2026 via #SFFS | 30 November 2026 | 30 November 2026 |
"Not submitted" does not mean "not needed". Form C-S figures come from finished accounts and a tax computation, IRAS can ask for both, and records must be kept for at least 5 years from the relevant YA. Our Form C vs Form C-S (Lite) guide goes deeper.
How to File in myTax Portal
- Fix the basis period and revenue. Use the financial year that ended in 2025 and measure revenue the way IRAS defines it.
- Finish the accounts and tax computation. Complete them before opening the return, whichever form you file.
- Set up Corppass. The filer needs the Approver role for "Corporate Tax (Filing and Applications)". A Preparer can complete Form C-S but cannot submit it.
- Pick the form. Open File Form C-S/ C in myTax Portal. At Form Type Selection, entering revenue of $200,000 or below under Form C-S brings up Form C-S (Lite).
- Complete the return. A qualifying company in its first 3 YAs claims the start-up tax exemption by answering "Yes" to the qualifying question in the return. Form C goes in with its supporting documents.
- Submit and save proof. Submit by 30 November 2026 and save the acknowledgement page.
To correct a filed Form C-S or Form C-S (Lite), use the Revise/ Object to Assessment digital service and attach the accounts and tax computation. Our corporate tax filing guide explains the computation.
What If the Company Was Dormant?
For tax purposes, a company is dormant only if it had no business and no income for the whole basis period. Even a little fixed deposit interest means a regular return for that YA.
Unless IRAS has waived filing, a dormant company still files by 30 November 2026. Check its status in myTax Portal under Account > Update Corporate Profile/ Contact Details:
- "No Business Done": a waiver is in place and no return is needed. If the company did restart or earn income in its 2025 financial year, use the Recommencement of Business form to request a return.
- "Active": file the Form for Dormant Company (two essential fields, no financial statements).
A company that will stay dormant can apply for a waiver, but every return up to the date business stopped must be filed. Our dormant company tax filing waiver guide sets out IRAS's four conditions. ACRA annual returns continue either way.
YA 2026 Deadlines and Extensions
Every YA 2026 return is due by 30 November 2026, even for a company with a loss or no income.
Extensions are narrow. Form C-S filed from accounting software under IRAS's #SFFS route (conditions apply) is automatically due by 15 December 2026; Form C and manual filings are not covered. Otherwise, the Request Extension of Time to File digital service opens for the current YA only after 30 November, and never once a court summons has been issued.
After the deadline, IRAS may issue an estimated Notice of Assessment payable within 1 month, offer composition of up to $5,000 per offence, send a section 65B(3) notice to a director, or summon the company or the people running it to court. Our company filing deadline calculator maps out your other dates.
Estimated Chargeable Income (ECI) is a separate filing due within 3 months of the year end, so the YA 2026 ECI should already be in (by 31 March 2026 for a 31 December 2025 year end). It is not needed if revenue is $5 million or below and ECI is nil. See our ECI filing guide.
Common Mistakes When Choosing the Form
- Counting interest as revenue. It is separate-source income.
- Calling a company dormant when it earned interest. Any income means a regular return.
- Using the $5 million concession twice. It covers one year of fluctuation.
- Leaving Corppass to the last week. Without an Approver, nobody can submit.
When to Get Professional Help
You may not need us. If the company qualifies for Form C-S (Lite) and its books are complete, filing it yourself is realistic. Get help for Form C, group relief or carry-back claims, incentive income, first accounts longer than 12 months, revenue near the $200,000 or $5 million lines, or overdue returns.
Tax Filing SG is run by ex-Big 4 Singapore Chartered Accountants (ISCA members). See our tax services; we quote once we have seen your accounts.
Frequently Asked Questions
Which companies can file Form C-S?
A company qualifies only if it meets all four IRAS conditions: it is incorporated in Singapore, its annual revenue is $5 million or below, all its income is taxable at 17% (one-tier exempt Singapore dividends and section 13(8) exempt foreign income are allowed), and it is not claiming loss carry-back, group relief, investment allowance, foreign tax credit or tax deducted at source. Every other company files Form C.
What is the revenue limit for Form C-S (Lite)?
The limit is revenue of $200,000 or below, measured as gross income from the principal activities, so interest and other separate-source income are excluded. The company must also meet every Form C-S condition. A company that qualifies may still file Form C-S or Form C instead.
When must a company file Form C instead of Form C-S?
A company must file Form C when it fails any Form C-S condition: it is incorporated outside Singapore or is a foreign company's branch, its revenue exceeds $5 million without the one-year concession, it has tax-exempt or concessionary-rate income, or it makes an excluded claim such as group relief.
Do I need to submit financial statements with Form C-S?
No. For Form C-S and Form C-S (Lite), the financial statements, tax computation and supporting schedules are prepared and kept, then sent only if IRAS asks. The exception is a section 19B writing-down allowance claim for intellectual property, which needs a Declaration Form through the Submit Document digital service. Form C, by contrast, is filed with them.
Can a dormant company skip Form C-S?
Only if IRAS has granted a filing waiver. The company's myTax Portal profile then shows "No Business Done". Otherwise it must file by 30 November 2026, although it can use the simplified Form for Dormant Company. A company that received any income, even fixed deposit interest, is not dormant and files a regular return.
My company was incorporated in 2025. Does it file for YA 2026?
Usually not. IRAS normally expects the first return 2 years after the year of incorporation, so a 2025 company first files for YA 2027. If it closed its first accounts in 2025 and started business or received income that year, it should request a YA 2026 return using the Request for Income Tax Return for Newly Incorporated Companies form. If its first accounts run past 12 months into 2026, it files YA 2026 and YA 2027 together by 30 November 2027.
Official Sources
- IRAS: Form C-S, Form C-S (Lite) and Form C overview
- IRAS: YA 2026 Form C-S explanatory notes (PDF)
- IRAS: Form C-S filing FAQs (PDF)
- IRAS: Guidance on filing the return
- IRAS: Dormant companies
- IRAS: Filing from accounting software (#SFFS)
- IRAS: Late filing of tax returns
- IRAS: Corporate Income Tax Filing Season 2026
Still unsure which corporate tax form your company should file?
Send us your revenue, year end and any claims on WhatsApp, and a Singapore Chartered Accountant will confirm which form you need and our fee for your case before you commit.
About Tax Filing SG — We are a Singapore accounting practice run by ex-Big 4 Singapore Chartered Accountants (ISCA). We handle accounting, corporate tax, GST and company secretarial work for Singapore SMEs, including overdue and late filings.
Last updated: 9 November 2026. This article is general information based on IRAS and ACRA guidance as at November 2026, not advice for your specific situation. Rules, rates and deadlines change, so check the official sources above or speak to us before acting.